Documentation: agent-skills coverage gaps

[Ethan-Arrowood]

Umbrella / parent issue for documentation gaps that block the @harperfast/skills rules from migrating to docs-driven generation. Repo-scoped workstream tracked here in documentation.

Why these matter: each of these rules currently has to stay hand-authored (mode: synthesized) because its canonical docs source is missing or thin. Writing the docs here lets the corresponding skill rule be generated from canonical content and stay in sync:

• Document the table → automatic REST endpoint mapping (and rest: true requirement) #538 (table → automatic REST endpoint mapping) → unblocks the adding-tables-with-schemas rule
• Add UI-independent reference for creating a Fabric account, organization, and cluster #539 (UI-independent Fabric account/cluster reference) → unblocks creating-a-fabric-account-and-cluster
• Add a reference page for the @harperfast/vite plugin (and fix stale package name) #540 (@harperfast/vite reference page) → unblocks the Vite half of serving-web-content (and relates to creating-harper-apps)

Sub-issues attached below.